Closed cell phenolic foam

ABSTRACT

A closed cell phenolic foam is formed from a phenolic resin, a blowing agent such as HCFC141b, a catalyst and less than 2.5% by weight relative to the resin of at least one hydrofluoroether or an azeotrope formulation thereof 1-methoxy-nonafluorobutane and especially an azeotrope formulation thereof with trans-1,2-dichloroethylene are preferred hydrofluoroethers. The phenolic foam has a stable closed cell content of greater than 90% and a stable thermal conductivity.

[0001] This invention relates to a closed cell phenolic foam and to a process for preparing such foams from resins.

[0002] Phenolic foams are widely used in building applications in view of their thermal insulation and fire resistant properties. Such phenolic foams are generally prepared by mixing a phenol formaldehyde resin with a blowing agent, a cell stabiliser and a hardener. EP-A-0170357 describes one such process for preparing a phenolic foam using Freon as a blowing agent, aqueous sulphuric acid as a hardener, and a cell stabiliser derived by oxylating castor oil with ethylene oxide or mixtures thereof with proplylene oxide. Freon is a particular chlorofluorocarbon (CFC). EP-A-0439283 describes the use of a complex blend of materials as an alternative blowing agent to a CEC. The blend comprises: at least one perfluoroalkane (PFA) (especially perfluoropentane, perfluorohexane or perfluoroheptane); and at least one component selected from a hydrogenated chlorofluorocarbon (HFC) and a specific alkane or cycloalkane.

[0003] EP-A-0579321 describes a phenolic foam including perfluro-N-methyl morpholine.

[0004] WO-A-9811715 describes the manufacture of resol foams using perfluorinated ethers as part of the blowing agent blend.

[0005] There is a need for an improved phenolic foam which is easily processed, environmentally friendly and has good thermal conductivity properties.

STATEMENTS OF INVENTION

[0006] According to the invention there is provided a closed cell phenolic foam formed from a phenolic resin, a blowing agent, a catalyst and at least one hydrofluroether or an azeotrope formulation thereof in an amount of less than 2.5% by weight relative to the resin to form a phenolic foam having a closed cell content of greater than 90% and a stable thermal conductivity.

[0007] Most preferably the hydrofluroether is present in an amount of from 0.5% to 1.5% by weight relative to the resin.

[0008] In a preferred embodiment of the invention the hydrofluoroether is of the general formula C_(a)F_(b)OCH₃ or C_(a)F_(b)OC₂H5 wherein:

b=2a+1

[0009] Preferably the hydrofluoroether is C₄F₉OCH₃ (1-methoxy-nonafluorobutane).

[0010] Ideally the hydrofluoroether is in an azeotrope formulation, especially with trans-1,2-dichloroethylene.

[0011] In a particularly preferred embodiment the azeotrope formulation is a 50/50 formulation of 1-methoxy-nonafluorobutane with trans 1,2, dichloroethylene.

[0012] The azeotrope formulation may be formed by a reaction of two or more components, at least one component being present in the phenolic resin.

[0013] The blowing agent may include a hydrogenated chlorofluorocarbon HCFC). Ideally, the HCFC is HCFC 141b (CCl₂F—CH₃).

[0014] Alternatively the blowing agent may include a hydrogenated fluorocarbon (HFC).

[0015] The foam may include an alkane or cycloalkane.

[0016] In a particularly preferred aspect the invention provides a closed cell phenolic foam formed from a phenolic resin, a blowing agent, a catalyst and less than 2.5% by weight relative to the resin of 1-methoxy-nonaflurobutane or an azeotrope formulation-thereof with trans-1, 2-dichloroethylene.

[0017] In a preferred aspect the invention provides a closed cell phenolic foam from a phenolic resin, HCFC 141 b (CCl₂F—CH₃) a catalyst and less than 2.5% by weight relative to the resin of 1-methoxy-nonaflurobutane or an azeotrope formulation thereof with trans-1, 2-dichloroethylene.

[0018] In an especially preferred aspect the invention provides a dosed cell phenolic foam formed from a phenolic resin, HCFC 1416 (CCl₂F—CH₃), a catalyst and less than 2.5% by weight relate to the resin of an azeotrope of 1-mehoxy nonaflurobutane with trans-, 2-dichloroethylene.

[0019] Preferably the catalyst is a strong mineral acid such as sulphuric acid containing at least 20% water, preferably at least 40% water.

[0020] The invention further provides a blend for forming a closed cell phenolic foam of the invention, the blend comprising a blowing agent, a catalyst and less than 2.5% by weight relative to a phenolic resin of at least one hydrofluroether or an azeotrope formulation thereof.

DETAILED DESCRIPTION

[0021] The invention will be more clearly understood from the following description thereof given by way of example.

[0022] The invention is based on the surprising finding that closed cell phenolic foams can be produced by using relatively small quantities of at least one hydrofluoroether (HFE). It is believed that the E acts as a surfactant.

[0023] Ethers are usually strong solvents which can have an adverse cell opening effect on foam and would therefore not normally be considered as suitable components for closed cell foams. We have however, surprisingly found that hydrofluoretheres can be effectively used as surfactants in foam formulations.

[0024] In addition to this unexpected use of such ethers, there is the further major advantage that these solvents have much less environmental impact than conventional solvents used in foam manufacture. Such solvents have a very low global warming potential when compared with conventional solvents used in such foam formulations.

[0025] Most importantly and unexpectedly we have found that not only is a highly closed cell foam produced using a hydrofluroether with a low global warning potential but also the foam produced has an extremely favourable stable thermal conductivity profile.

[0026] The closed cell value may be measured by the method described in B.S. 4370/ASTM D2856. The foam of the invention has a dosed cell content of greater than 90% when measured by this method.

[0027] The K value is measured as described in method 7A of B.S. 4370 part 2 with reference to BS3927. ASTM C177 is equivalent. The preferred foam of the invention has a K value at 30 days or longer of less than about 0.018 W/M° C. Even more surprisingly the thermal conductivity remains stable when tested at high temperatures of about 70° C. over prolonged periods.

Example 1

[0028] A phenolic resin was used which was prepared from the ingredients and using the process described in Examples 1 to 3 of EP-A-0170357. This specification is incorporated herein by reference.

[0029] Foams were manufactured in the laboratory using the formulations below. The chemicals were mixed using a high speed laboratory stirrer and dispensed into a mold having a volume as approximately 0.03m³. The mold was subsequently placed in an oven at 70° C. for a minimum of 3 hours. After demolding, the foam was allowed to cool down to ambient temperature prior to commencement of thermal conductivity testing. Foam A Foam B (pbw) (pbw) Phenolic resin 100 100 Blowing agent HCFC 141b 10 10 HFE 7100 0.54 0 Catalyst* 12 12

[0030] Thermal conductivity testing was performed at ambient and at 70° C. and the results are shown in the Table below. It is very clear that without the HFE surfactant, the drift in thermal conductivity is very rapid both at ambient and 70° C. whilst with HFE 7100 as surfactant, the thermal conductivity drifts to a value in the region of 0.018 W/M°K-W/M°K. THERMAL CONDUCTIVITY (W/M° C. at 10° C.) Days 1 4 15 17 42 Foam A Ambient 0.0168 0.0184 70° C. 0.0159 0.0179 0.0193 Foam B Ambient 0.0184 0.0304 70° C. 0.0291 0.0298

[0031] HFE 7100 is 1-methoxy-nonafluorobutane having the formula C4H₉OCH₃. It has a boiling point of 60° C.

EXAMPLE 2

[0032] Discontinuous block foam, was manufactured on a commercial scale plant to produce blocks of dimensions of approximately 2440×1000×1000 mm. The foam mix was dispensed through a low pressure mixer into a heated mold. The product was put through a three hour curing cycle prior to demold. The foam was manufactured according to the following formulation. amount Phenolic resin (example 1): 100 pbw Blowing agent: HCFC 141b 10.8 pbw HFE 71 DE 1.2 pbw Catalyst*: 11.68 pbw colour: KDS black 0.3 bw

[0033] The density of the foam thus formed was 35 kg/m³.

[0034] HFE 71 DE is a 50/50 blend of HFE 7100 with trans 1, 2 dichloroethylene of the formula CHCl.CHCl. The material is available from 3M. The particular advantage of this material is that it is an azeotrope and boils at 40° C. which gives good processing characteristics, especially in producing a laminated product.

[0035] We have found that these foams have excellent thermal conductivity stability as follows: Thermal Conductivity W/M° C. at 10° C. Condi- On tioning manufacture 7 days 21 days 42 days 63 days 90 days Ambient 0.0166 0.0146 0.0147 0.0156 0.0166 0.017  +70° C. — 0.0151 0.0168 0.0171 0.018  0.0182

EXAMPLE 3

[0036] Using tie method described in Example 2 a foam was manufactured according to the following formulation. Amount Phenolic Resin (Example 1) 100 pbw Blowing Agent: HCFC 141b 10.8 pbw HFE 71 DE 1.2 pbw Catalyst* (Example 2) 11.7 pbw Colour: KDS Black 0.3 pbw

[0037] The density of the foam thus formed was 35 kg/m³.

[0038] The foam of this example has excellent thermal conductivity stability as follows. Thermal Conductivity W/M° C. at 10° C. Condi- tioning Initial 7 days 21 days 42 days 63 days 125 days Ambient 0.0167 0.0146 0.0157 0.0157 0.0159 0.0174 +70° C. — 0.0134 0.0152 0.0165 0.0174 0.0180

EXAMPLE 4

[0039] Using the method described in Example 2 a foam was manufactured according to the following formulation. Amount Phenolic resin (Example 1) 100 pbw Blowing agent: HCFC 141b 10.8 pbw HFE 71 DE 0.57 pbw Catalyst (Example 2) 11.7 pbw Colour: KDS black 0.3 pbw

[0040] The density of the foam thus formed was 35 kg/N³.

[0041] The foam of this example has excellent thermal conductivity stability as follows: Thermal Conductivity W/M° C. at 10° C. Condi- tioning Initial 7 days 21 days 42 days 63 days 125 days Ambient 0.0151 0.0149 0.0160 0.0155 0.0167 0.0174 +70° C. — 0.0138 0.0153 0.0165 0.0180 0.0180

[0042] Typical global warming potentials for perfluoroalkanes are as follows: CF₄ 6500 C₂F₆ 9200 C₃F₈ 7000 C₅F₁₂ 7500 C₆F₁₄ 7400

[0043] This is in complete contrast to EYE 7100 which has a global warming potential of 500 and especially EE 71DE which has a global warming potential of 250. Thus, the use of HFE's in phenolic foam formulations has considerable environmental advantages compared with perfluoroalkanes.

[0044] It is envisaged that the HCFC's used in the phenolic foam blowing agent blend of the invention may be selected, for example, from one or more of: HCFC 141b CCl₂F—CH₃ HCFC 142b CH₃CClF₂ HCFC 123 CF₃—CHCl₂ HCFC 124 CHClF₂ HCFC 225ca CHCl₂—CF₂CF₃ HCFC 225cb CClF₂—CF₂CHClF

[0045] It is also envisaged that the blowing agent blend may include a suitable hydrogenated fluorocarbon selected, for example, from one or more- of- HFC 125 CHF₂—CH₃ HFC 134 a CF₃CH₂F HFC 152 a CH₃—CHF₂ HFC 245fa CF₃—CH₂CHF₂ HFC 365mfc CF₃—CH₂—CF₂—CH₃

[0046] The HFC's may be represented by the formula C_(R)H_(P)F_(Q) whenever:

[0047] R is an integer from 1 to 4

[0048] P is an integer from 1 to 5

[0049] and Q=(2R+2)−P for an open chain HFC and (2R−P) for a cyclic HFC.

[0050] It is further envisaged that the phenolic foam blowing agent blend may include an alkane, especially n-pentane, or a cycloalkane, especially cyclopentane.

[0051] The invention is not limited to the embodiments hereinbefore described which may be varied in detail. 

1. A closed cell phenolic foam formed from a phenolic resin, a blowing agent, a catalyst and at least one hydrofluroether or an azeotrope formulation thereof in an amount of less than 2.5% by weight relative to the resin to form a phenolic foam having a closed cell content of greater than 90% and a stable thermal conductivity.
 2. A foam as claimed in claim 1 wherein the hydrofluroether is present in an amount of from 0.5% to 1.5% by weight relative to the resin.
 3. A foam as claimed in claim 1 wherein the hydrofluoroether is of the general formula C_(a)F_(b)OCH₃ or C_(a)F_(b)OC₂H₅ wherein: b=2a+1
 4. A foam as claimed in claim 1 wherein the hydrofluoroether is C₄F₉OCH₃ (1-methoxy-nonafluorobutane).
 5. A foam as claimed in claim 1 wherein the hydrofluoroether is in an azeotrope formulation.
 6. A foam as claimed in claim 5 wherein the hydrofluoroether is in an azeotrope formulation with trans-1,2-dichloroethylene.
 7. A foam as claimed in claim 6 wherein the azeotrope formulation is a 50/50 formulation of 1-methoxy-nonafluorobutane with trans 1,2, dichloroethylene.
 8. A foam as claimed in claim 5 wherein the azeotrope formulation is formed by a reaction of two or more components, at least one component being present in the phenolic resin.
 9. A foam as claimed in claim 1 wherein the blowing agent includes a hydrogenated chlorofluorocarbon (HCFC).
 10. A foam as claimed in claim 9 wherein the HCFC is HCFC 141b (CCl₂F—CH₃).
 11. A foam as claimed in claim 1 wherein the blowing agent includes a hydrogenated fluorocarbon (HFC).
 12. A foam as claimed in claim 1 wherein the blowing agent includes an alkane or cycloalkane.
 13. A closed cell phenolic foam formed from a phenolic resin, a blowing agent, a catalyst and less than 2.5% by weight relative to the resin of 1-methoxy-nonaflurobutane or an azeotrope formulation thereof with trans-1, 2-dichloroethylene.
 14. A closed cell phenolic foam formed from a phenolic resin, HCFC 141 b (CCl₂F—CH₃), a catalyst and less than 2.5% by weight relative to the resin of 1-methoxy-nonaflurobutane or an azeotrope formulation thereof with trans-1, 2-dichloroethylene.
 15. A closed cell phenolic foam formed from a phenolic resin, HCFC 141b (CCl₂F—CH₃), a catalyst and less than 2.5% by weight relative to the resin of an azeotrope of 1-methoxy nonaflurobutane with trans-1, 2-dichloroethylene.
 16. A closed cell phenolic foam as claimed in claim 1 wherein the catalyst is a mineral acid containing at least 20% water.
 17. A closed cell phenolic foam as claimed in claim 14 wherein the catalyst is a mineral acid containing at least 20% water.
 18. A closed cell phenolic foam as claimed in claim 15 wherein the catalyst is a mineral acid containing at least 20% water.
 19. A blend for producing a closed cell phenolic foam as claimed in claim 1, the blend comprising a blowing agent, a catalyst and less than 2.5% by weight relative to a phenolic resin of at least one hydrofluroether or an azeotrope formulation thereof.
 20. A blend for producing a closed cell phenolic foam as claimed in claim 14, the blend comprising HCFC 141 b (CCl₂F—CH₃), a catalyst and less than 2.5% by weight relative to the resin of 1-methoxy-nonaflurobutane or an azeotrope formulation thereof with trans-1, 2-dichloroethylene.
 21. A blend for producing a closed cell phenolic foam as claimed in claim 15, the blend comprising HCFC 141b (CCl₂F—CH₃), a catalyst and less than 2.5% by weight relative to the resin of an azeotrope of 1-methoxy nonaflurobutane with trans-1, 2-dichloroethylene. 